The invention relates to a hand-held power tool. The hand-held power tool may be realized, for example, in the form of a hammer drill or an impact screwdriver. For example, the tangential striking mechanism may generate an impact screwing motion of the output shaft. In that case, the tool may be configured in the form of a screwdriver, which can execute an impact screwing motion in the tool receptacle via the rotating and partially percussive motion of the output shaft. The tangential striking mechanism is normally driven via a motor, if applicable with the interconnection of a gear mechanism. The main components of a tangential striking mechanism structured in a coupling-like manner are a hammer allocated to a drive shaft of the coupling and an anvil allocated to an output shaft of the coupling. The hammer is able to remove itself axially from the anvil against the application of the force of a spring with twisting of the same and subsequently, again with twisting of the same and accelerated under the application of the force of the spring, move percussively against the anvil. The impact motion takes place practically in the tangential direction of the rotational movement. The rotational movement and axial back-and-forth movement for executing a rotary impact are coupled by a sliding block guide so that the hammer is ultimately moved in a restraint-guided manner according to the requirements of the sliding block guide. At a reversal point of the back-and-forth movement, the hammer is triggered by the anvil. At another reversal point of the back-and-forth movement, the hammer executes a rotary impact against the anvil. In this way, the hammer is able, for example, to strike the anvil at every half revolution practically in the tangential direction of the rotational movement and transmit comparatively high torque peaks with the rotary impact. These types of high torque peaks would normally not be achievable with a continuous rotary drive of the output shaft. An aforementioned tangential striking mechanism may be designed as a resonant spring-mass system with a comparatively narrowly defined torque range, within which the actual operating point is established by a drive speed of the drive for the drive shaft. The operating point is also characterized by a triggering moment, at which the hammer decouples from the anvil in the trigger position, i.e., the triggering moment when executing a separation of an engagement of the anvil and of the hammer. In addition, the operating point is characterized by the high torque peak that can be transmitted during the impact. Significant for this are, among other things, the moment of inertia of the hammer, the spring stiffness of the spring and the transmission function of the sliding block guide, which is ultimately specified by a control contour of the sliding block guide.
Within the scope of usual applications, a tangential striking mechanism has a comparatively low triggering moment, which is achieved by means of a comparatively low spring stiffness. A drilling of, for example, deep holes having large diameters that require high torques is only conditionally possible when using such a standard tangential striking mechanism.
It would be desirable to design a tangential striking mechanism also for applications having comparatively high torque requirements. Simply scaling up the design parameters of a standard tangential striking mechanism does not produce the objective in this case, because this regularly goes hand in hand with an increase in the body masses of the tangential striking mechanism. In the case of a power tool of the type cited at the outset, this would result in a deterioration of handling.
The object related to the hand-held power tool is attained by the invention with a hand-held power tool of the type cited at the outset, in which it is provided according to the invention that the sliding block guide have a helical control contour, which has a first slope in a first section and a second slope in a second section, wherein the first and second slopes are different.
It is preferred that a first gradient angle α of the first slope measured in relation to an axis of a cylindrical body for the sliding block guide is greater than a second gradient angle β of the second slope measured in relation to the axis. The slopes have in particular the same algebraic sign, i.e., the sections are part of a single helical progression of the control contour.
In an especially preferred further development, it may be provided that the first section forms an anvil-proximal section and the second section forms an anvil-distal section of the control contour and the first slope is greater than the second slope. In particular, the first and the second slopes may be the only essentially different slopes of the control contour. In other words, except for a transition area that is as continuous as possible, there are virtually only the first and second sections having essentially different slopes. The first and second sections are preferably directly adjacent to one another.
The invention proceeds from the consideration that a tangential striking mechanism for a user-friendly and comparatively light-weight hand-held power tool should have a spring system with comparatively low spring stiffness. Proceeding herefrom, it was further recognized that a comparatively high triggering moment is nevertheless achievable if a sliding block guide, especially in a first section in this case that is allocated to the impact, be preferably designed to be suitably steep. It was also recognized that to transmit a comparatively high torque peak with an impact between the hammer and the anvil, a sliding block guide, especially in a second section in this case that is allocated to the triggering of the hammer and the anvil, be preferably designed to be suitably flat. The invention basically recognized that a first section allocated to the impact and a second section allocated to the triggering may be provided with a different first and second slope of a helical control contour.
In contrast to a standard control contour, e.g., a uniform helical control contour applied to a spindle that has a constant slope over the entire progression of the control contour, the idea of the invention provides a sliding block guide with a helical control contour that has a varied slope in an adapted manner. This control contour adapted in the above-mentioned manner has a different slope in a first section allocated to the torque transmission than in a second section allocated to the triggering of the hammer and the anvil. The sliding block guide may preferably also have a control contour basically designed to be V-like, i.e., double helically. However, in contrast to a previously known control contour, this is provided with a single continuously aligned helical progression in a V-leg, which in addition has a first slope in a first section of the V-leg and a second different slope in a second different section of the V-leg, with the slopes having the same algebraic sign.
A comparatively good impact as well as a comparatively high triggering moment may be achieved with a helical control contour of the sliding block guide adapted in this way and this advantageously without the mass of the tangential striking mechanism having to be increased. In particular, a spring stiffness may nevertheless be kept comparatively low.
Additional advantageous further developments of the invention can be found in the dependent claims and provide in detail advantageous possibilities of realizing the concept explained above within the framework of the stated problem as well as with respect to additional advantages.
The anvil is preferably connected to be one piece with the output shaft and the spindle to be one piece with the drive shaft. The sliding block guide is preferably formed on a cylindrical body such as a shaft, e.g., spindle, or a hollow body, for example, on an outer side or an inner side of the cylindrical body. These measures, individually or in combination, produce an especially compact and stable tangential striking mechanism.
The sliding block guide preferably has a first control contour on a spindle between the drive shaft and output shaft. Alternatively, preferably additionally, the sliding block guide has a second control contour on an inner side of the jacket of the hammer. In particular, because of the interplay of the aforementioned first and second control contours in a preferred sliding block guide, an axial and rotating movement of the hammer against the anvil may be realized in order to advantageously execute a rotary impact movement.
With a further development, only the first control contour or only the second control contour of the sliding block guide may respectively have a first section having the first slope and a second section having the second different slope. In a modification, the first control contour and the second control contour of the sliding block guide may respectively have a first section having the first slope and a second section having the second different slope.
The first section preferably forms (in particular respectively) an anvil-proximal section and the second section forms anvil-distal section of the control contour. The first slope is preferably greater than the second slope. In particular, a first gradient angle α of the first slope measured in relation to an axis of a cylindrical body for the sliding block guide is greater than a second gradient angle β of the second slope measured in relation to the axis. In an especially advantageous manner, an increased triggering moment can be achieved with the tangential striking mechanism, and the tangential striking mechanism is nevertheless in a position to transmit a comparatively high torque peak, i.e., to execute a good impact. The control contour guarantees an especially secure and loss-free transmission of force in the tangential striking mechanism acting as a coupling. The tangential striking mechanism is also suitable in an especially preferable manner for executing work requiring high torques.
It has proven to be especially advantageous that the first and second slopes are the essentially only different slopes of the control contour and the first and second sections are directly adjacent to one another. This produces a comparatively simple design of the control contour. Basically, beyond this, another section may be provided between the first and second sections, which is provided as a transition section with a gradual adjustment of slope or which has a value that is constant between the first and second slopes.
In an especially advantageous further development, the control contour, preferably a first control contour, is formed by a closed slider of the sliding block guide. In an especially preferred design, a closed slider is configured in the form of a groove (e.g., with a U-shaped cross-section), wherein a sliding block connected in a restraint-guided manner to the hammer can be moved in the groove.
In a further especially advantageous further development, the control contour is formed by an open slider of the sliding block guide. The second control contour is especially preferably formed by an open slider of the sliding block guide. In an especially preferred design, an open slider is configured in the form of a running surface (with a flat cross-section), wherein a sliding block connected in a restraint-guided manner to the hammer can be moved on the running surface.
In an especially preferred further development, which is also explained on the basis of an embodiment, the sliding block guide is formed by an interplay of a closed slider on a spindle between the drive shaft and output shaft and an open slider on an inner side of the jacket of the hammer. Alternatively, the sliding block guide may also be formed by an interplay of a closed slider on an inner side of the jacket of the hammer and an open slider on a spindle between the drive shaft and output shaft. These types of a sliding block guide made of a combination of a closed and an open slider have proven themselves in particular.
Within the framework of an aforementioned especially preferred further development, the control contour is configured in the form of a groove of the running surface, wherein a sliding block can be moved in a restraint-guided manner on the control contour. Basically, the control contour may also be formed inversely thereto, e.g., with a web, on or at which a sliding block is restraint-guided. Basically, a control contour of a sliding block guide for realizing a suitable transmission function may be carried out with two different slopes in a manner adapted to the design requirements.
The first section preferably forms an anvil-proximal section and the second section forms an anvil-distal section of the control contour, wherein the first slope is preferably greater than the second slope. In other words, the first slope allocated to the transmission of the torque peak during the impact is greater than the second slope of the control contour allocated to the triggering of the hammer and the anvil, in particular with a first control contour located on the spindle.
Within the framework of such a further development, it was recognized that a torque peak of a comparatively high amount can be transmitted if the greatest possible portion, in particular the entire rotational energy of the hammer, is transformed into impact energy of the rotary impact (also called tangential impact), i.e., transformed into a torque. This may be supported by a comparatively flat design of the control contour measured in relation to an axis. Within the framework of another further development, it was recognized that a triggering moment between the anvil and the hammer can be designed to be comparatively high. This may also be supported by a comparatively steep design of the control contour measured in relation to an axis.
The first slope preferably increases in the first anvil-proximal section. The increase may be implemented gradually. The first section having a greater slope may also be configured in the form of a first anvil-proximal section having a constant slope, which is greater than the second slope in the second anvil-distal section. The second slope of the control contour is comparatively low. In this case, the progression of the slope in the second section may decrease gradually. However, the second section may also be designed comparatively simply as a section with a constant second slope, which is less than a first slope in the first section. In particular, a progression of the slope in the transition from the first to the second sections may be designed to be gradual or stepped or as a simple stage between the first and second slopes.
In particular, it is provided that, in the engagement position of the anvil and of the hammer for executing a tangential impact, a sliding block connected in a restraint-guided manner to the hammer is disposed in the first section of the control contour. This advantageously rules out that a transmission of a torque peak is limited by a force absorption causing resistance in the second section having a lower second slope. In fact, it is guaranteed that the sliding block facilitates and does not counteract the transmission of the full rotational energy of the hammer as torque on the anvil in the area of the comparatively greater first slope.
The anvil and the hammer are preferably in the complete engagement position to execute a tangential impact. In a reversal point of the back-and-forth movement of the hammer where the rotary impact is executed, the anvil and the hammer have an engagement area, which may be specified, for example, by the length of the impact means. It is preferably provided that the first section especially having a greater slope has an axial extension which makes up at least 20% of the axial extension of the engagement area. This ensures that at least on the remaining 20% of the axial extension of the engagement area, an advantageously greater first slope is present, which permits a transmission of especially high torque peaks. The result during the impact tends to improve, the greater the axial extension of the first section. The axial extension of the section advantageously makes up at least 20% of the axial extension of the engagement area or corresponds approximately to the extension of the engagement area without exceeding it however.
It has also proven to be advantageous that at least in the trigger position of the anvil and of the hammer for executing a separation of an engagement of the same, a sliding block connected in a restraint-guided manner to the hammer is disposed in the second section of the control contour. In this way, it is ensured that the sliding block permits only a high triggering moment in consideration of the lower second slope of the sliding block guide.
An impact means is formed in the case of the anvil and/or hammer preferably in the form of at least one cam. Two cams have proven to be especially advantageous. The cams are advantageously formed on a ring circumference of the anvil and/or the hammer. The ring circumference can be disposed on the head side or laterally from the anvil and/or hammer. The further development having two cams permits, with a suitable adaptation of the control contour, a triggering or tangential impacting of the hammer and the anvil with every half revolution. With a further suitable adaptation of the sliding block guide, more than two cams may be provided, for example in the form of a ring gear. In particular, this may limit a rotational movement to a fractional amount of a full revolution of the hammer.
Within the framework of an especially preferred use of the tangential striking mechanism, a hand-held power tool may be configured in the form of a hammer drill. The tangential striking mechanism is preferably designed to execute the function of a sliding clutch. In this use, the tangential striking mechanism may be preferably operated also out of resonance of the corresponding spring-mass system. The second slope in the second anvil-distal section of the control contour is preferably designed such that the tangential striking mechanism has an especially high triggering moment in order to allow the normal drilling operation of the hammer drill, i.e., not to trigger during the normal drilling operation.
In a modified further development of a use, it has proven to be advantageous to design the hand-held power tool in the form of an impact screwdriver. In the case of this further development, the tangential striking mechanism is designed to execute the function of an impact screwing motion. In this case, it has proven to be especially advantageous for the tangential striking mechanism to be designed for a resonant operation of the spring-mass system connected therewith. This may occur for a defined comparatively limited torque range. In particular, the first slope in the first anvil-proximal section is designed with a comparatively high value in order to achieve an especially high torque peak transmission in the case of a rotary impact between the hammer and the anvil.
An adaptation of the control contour in accordance with the idea of the invention is especially advantageous for the two aforementioned cases of a use. In addition, the aforementioned cases of a use may also be combined with one another by an optimized adaptation of both the first section having a comparatively greater slope as well as the second section having a comparatively lower slope. As a whole, the design of a needs-adapted tangential striking mechanism is possible which permits the transmission of high torque peaks in the case of a rotary impact, on the one hand, and operation with high torque requirements below a triggering moment of the tangential striking mechanism, on the other. In particular, a triggering moment of the tangential striking mechanism may be designed to be comparatively high by increasing the first slope in the first anvil-proximal section so that the tangential striking mechanism behaves practically like a sliding clutch. Nevertheless, a comparatively good torque transmission is guaranteed in the anvil-distal section.
Exemplary embodiments of the invention are described in the following on the basis of the drawings. These drawings are not necessarily supposed to represent the exemplary embodiments to scale, rather the drawings are executed in a schematic and/or slightly distorted form when it is useful for explanatory purposes. Reference is made to the pertinent prior art with respect to additions to the teachings directly identifiable from the drawings. It must be taken into consideration in this case that a wide range of modifications and changes related to the form and detail of an embodiment may be undertaken without deviating from the general idea of the invention. The features of the invention disclosed in the description, the drawings as well as in the claims may be essential for the further development of the invention both separately as well as in any combination. Moreover, all combinations of at least two features disclosed in the description, the drawings and/or the claims fall within the scope of the invention. The general idea of the invention is not restricted to the exact form or detail of the preferred embodiments described and depicted in the following or restricted to a subject matter which would be limited as compared to the subject matter claimed in the claims. In the case of any dimensioning ranges given, values within the stated limits are also meant to be disclosed as limit values, and be applicable at will and claimable.
Additional advantages, features and details of the invention are disclosed in the following description of the preferred exemplary embodiments as well as on the basis of the drawings.